Knowledge Base

The forthcoming Broadband Forum G.fast Certification Program, based on the ID-337 test plan, presents a number of unique challenges, including requirements for testing multiple CPEs (customer premise equipment) connected to a DPU (demarcation point unit) using a multi-pair cable. This white paper describes an approach to the construction of a copper cable plant...

The presence of crosstalk is a major detriment to the performance of Digital Subscriber Line (DSL) transceivers. It is therefore important to test performance under a wide variety of crosstalk scenarios. This thesis presents the development of a crosstalk noise generation system as a tool for DSL performance testing. Where many commercially available solutions are limited to specific testing needs, the system presented here is universal and can simulate virtually any noise scenario conceivable for DSL deployment.
Several requirements for the accurate frequency domain modeling of DSL crosstalk are presented. The time domain properties of crosstalk were also studied with particular attention paid to the amplitude distribution. The importance of a Gaussian amplitude distribution and the limiting effect of a finite-length pseudo-random crosstalk sequence on the "tail" of the Gaussian distribution were investigated. A method of forcing finite-length crosstalk sequences to have a "near-Gaussian" amplitude distribution is proposed.

From back cover: "Digital Subscriber Lines (DSLs) have transformed millions of ordinary phone lines into broadband arteries that link homes and businesses to the Internet at megabit speeds. DSL Advances brings together the state-of-the-art in DSL technology and architecture for every technical professional and manager. The authors of the classic Understanding Digital Subscriber Line Technology review the key challenges service providers and equipment manufacturers face now, preview tomorrow's most important standards and technical enhancements, and offer new insights into today's regulatory and business environment."

From the preface: "The third edition of Digital Communications has undergone a major reorganization. Compared with with the second edition, which had eight chapters, the third edition contains fifteen. Chapter 1 (Introduction) and Chapter 15 (Multiuser Communications) are new. Other new material that has been added includes a treatment of run-length-limited codes, Nakagami fading statistics, trellis codeing for fading channels, multicarrier modulation, and an expanded treatment of blind equalization. Since this is an introductory-level text, the treatment fo these topics is limited in scope. Some topics that were in the second edition have been deleted, including echo cancellation and suppression of narrowband interference in spread spectrum signals."

This tutorial provides an overview of ADSL technology and focuses on the physical layer as defined in ANSI T1.413-1998. From the introduction: "The demand for high-speed data networks in the "last mile" has driven the need for robust, interoperable, and easy to use multi-vendor Digital Subscriber Line (DSL) access solutions. DSL collectively refers to a group of technologies that utilize the unused bandwidth in the existing copper access network to deliver high-speed data services from the distribution center, or central office, to the end user. DSL technology is attractive because it requires little to no upgrading of the existing copper infrastructure that connects nearly all populated locations in the world. In addition, DSL is inherently secure due to its point-to-point nature."

From the back cover: "The basic infrastructure for the global broadband network of the future is already in place in most homes and offices. Ordinary telephone lines can provide low-cost, high volume access to the exploding world of telecommunications services that users increasingly rely on. Now, leading experts in the field hve come together to share their insights in a single volume, explaining the past, present, and future of all the DSL technologies."

This presentation provides an overview the ITU-T G.994.1 (G.hs) Handshaking Procedures for Digital Subscriber Line Transceivers standard. The overview covers the physical layer modulation (DPSK), frame structures, message structures, and parameter encoding. The presentation also includes examples of the differential encoding used for the modulation, and the delimiting bits used within the parameter tree.

This presentation provides an overview and introduction to Voice over DSL (VoDSL) technologies. The presentation covers the basics of channels voice over DSL, Voice over ATM (VoATM) and Voice over IP (VoIP). The presentation also includes a quick introduction to BLES, which is used to transport voice of AAL2 over ATM.

From the back cover: "I wrote this book for those of us in the world's most exciting industries - telecommunications, networking and the Internet. I deliberately didn't write a book that only geeks could understand. I wrote a business book that you and I could understand. I explain the technical concepts in non-technical , business language that anyone in business (whether buying, selling or investing) should be able to understand. Some of my definitions are short. Some are encyclopedic. My focus is 720 practical. What the term means. What the technology does. What benefits the technology confers. which pitfalls to watch for. Use this book in your day-to-day business life. Dip into it before a meeting with a vendor, a customer, a broker or a boss. I've got 19 years in this book. My readers and my contributing editor, Ray Horak, have contributed enormously over the years. By now, all of us have made this dictionary pretty darn good. I'm proud of this edition."

From the back cover: "Digital Subscriber Line technology heralds the age of digital communication, providing a faster, more efficient method of transmitting data over regular telephone lines. The widespread adoption of DSL technology increases the demand for subject-specific, in-depth knowledge of this breakthrough in digital communication. DSL: Simulation Techniques and Standards Development for Digital Subscriber Line Systems arms the communications and networking engineer with the quintessential information for implementing DSL systems . . . "

From the back cover: "Signal processing and noise reduction are at the core of telecommunications and information processing systems. With the increasing use of digital cellular mobile systems in a variety of adverse environments, noise reduction is becoming a particularly important aspect of communication system design. This second edition provides a thoroughly revised and expanded introduction to the fundamentals of random processes, Bayesian modelling, and noise reduction. The subject is covered in a graphical and mathematically accessible manner with the emphasis on Bayesian inference and its application to noise reduction."

From the back cover: "PPP Design, Implementation, and Debugging, Second Edition, is a complete and convenient resrouce for netowrk system designers and administrators. This book contains everything you need to know to work with the Point-to-Point Protocol (PPP), one of the most important Internet protocols in use today. Inside you'll find clear explanations of the underlying concepts, practical implementation information, and valuable debugging techniques to keep your PPP connections running smoothly, efficiently, and uninterrupted."

Broadband Forum is an international industry consortium of nearly 200 leading service providers, equipment manufacturers and other interested parties, focused on developing the full potential of broadband DSL to meet the needs of the mass market.

The performance of DSL transceivers can be impaired by interference from other transceivers operating over wires in the same binder group. It is therefore important to test DSL transceivers in the presence of crosstalk, which can be simulated in a programming environment such as MATLAB. The simulated crosstalk can then be exported to an arbitrary waveform generator (AWG) for injection onto the line through a high-impedance noise injection circuit. This document describes a method of crosstalk simulation and calibration whereby white gaussian noise (WGN) is passed through a frequency-domain filter that gives the noise the spectral characteristics of crosstalk. The crosstalk is calibrated by measuring its power with a vector signal analyzer (VSA) and adjusting the output level on the AWG to achieve the desired noise power. By using MATLAB to estimate the simulated crosstalk power in the same manner as the VSA, the calibration can be performed in MATLAB without taking actual measurements.

One of the most commonly deployed DSL variants is ADSL. Despite this fact, deployment of new robust and reliable ADSL services is increasingly difficult due, in part, to the physical limitations of the copper telephone system infrastructure, and also in part to the lack of useful ADSL network debugging tools. ADSL service providers and technicians currently lack a device capable of decoding physical layer signaling and displaying actual physical layer parameters and statistics associated with a live ADSL connection, independent of the end stations. Similar devices used in other network technologies are often referred to as protocol analyzers. The intent of this paper is to illustrate how Matlab [1], in conjunction with a DSP or a PC, can be used to create an effective ADSL handshaking protocol analyzer based on ITU-T G.994.1 (G.hs) [2]. G.hs conformance is critical in establishing a successful ITU-T G.992.1 (G.dmt) [3] based ADSL connection.

The issue of radio frequency interference in Digital Subscriber Line (DSL) networks is of particular concern in urban areas with many strong radio sources nearby. This paper investigates in detail the mechanisms underlying the capacity reduction due to the presence of radio frequency signals from Amplitude Modulated (AM) broadcast stations in an ADSL network. An ADSL system, channel, and radio frequency interference noise were simulated in MATLAB. The capacity reduction due to different Radio Frequency (RF) ingress conditions was studied. Spectral Spreading of the RF interferer, as suggested by Harris et al [1], is a primary cause of capacity reduction, but only at long loop lengths where the signal to Gaussian noise ratio is very low.

The issue of radio frequency interference in Digital Subscriber Line (DSL) networks is of particular concern in urban areas with many strong radio sources nearby. Prior work by Harris et al showed drastic decreases in DSL link capacity with a narrowband AM interferer. The purpose of this thesis was to investigate in more detail the mechanisms underlying the capacity reduction observed by Harris. In this thesis, an ADSL system, channel, and radio frequency interference noise were simulated in MATLAB. The capacity reduction due to different RF ingress conditions was studied. It was found that a narrowband interferer does not cause a drastic decrease in capacity if time and frequency domain equalizers are employed in the receiver. Contrary to Harris?s suggestions that spectral spreading of the interferer is the primary cause of capacity reduction, it is shown in this thesis that such spreading is a secondary effect and that the unequalized channel is the predominant source of capacity reduction.

A protocol analyzer is a device that non-intrusively monitors bi-directional communications on a link, demodulates the physical layer signals, and captures the raw binary data for subsequent state and timing analysis. There are no commercial products currently available that perform this function for ADSL link initialization procedures. In this project, a MATLAB application was developed that enables capture (via a digital sampling oscilloscope) and protocol analysis of the first segment, known as handshaking, of the ADSL link initialization procedure. The protocols of interest are ITU-T G.994.1 (G.hs), which defines the activation and handshaking procedures used by complaint ADSL equipment, and ITU-T G.992.1 (G.dmt), which defines the physical layer requirements of ADSL equipment utilizing the Discrete Multi-Tone (DMT) line code.

InterOperability is becoming increasingly important in today?s communication industry. In a time when the consumer has more choice and flexibility in their home networking and Internet services than ever before, single vendor solutions are nearly impossible and most definitely impractical. For this reason manufacturers are taking every precaution to make sure their products work properly with all other manufacturers? products. In this spirit standards bodies are formed with the claim that modems will work collectively if they adhere to the approved standard. However, as with all documents the standards are open to interpretation. This test suite will ensure complete activation phase compliance of a High Bit Rate Digital Subscriber Line- Second Generation modem. The tests are designed to scrutinize the modems adherence to American Nation Standards Industry?s Ti.418-2000 High bit rate Digital Subscriber Line- 2nd Generation (HDSL2) approved standard. All anticipated results are based on this document and the validity of the anticipated results can be proved using this document. The methods of testing are as low level as possible and do not rely on a specific vendor?s product so the most accurate and unbiased results may be obtained.